Page 75 - Advanced Mine Ventilation

58 Advanced Mine Ventilation

Table 4.6 Air Quantities for Nonworking Areas

3 2
25 ft /min/ft of the Cross Section
Stone Drifts Allow for Leakage in Ducts
Pump houses 5000 cfm
Battery charging station 10,000 cfm
a 3
Diesel locomotive 100e140 ft /min/bhp

a
US requirements are more restrictive based on diesel particulate emissions. They will be discussed in Section 4.2.
Table 4.7 Optimum Air Velocities in Coal Mines

Location Optimum Air Velocity (ft/min)
Working faces 150e500 (use gas layering index to guide)
Conveyors/loading points Less than 600
Main airways Less than 1000
Shafts 1500e2000
Fan drifts Less than 2500

4.10 Standards of Volumetric (Ventilation) Efficiency

A final check on the estimation of ventilation air quantities is done by a well-
established criterion, the volumetric/ventilation efficiency. It is defined as the ratio
of air quantities required on the working faces/total air quantity at the fan(s). For
well-designed ventilation systems, it ranges from 44 to 55% for workings laid out
in the coal seam. For horizon mining, it can be even higher at 55 to 65%.
An example:
Let us suppose the mine layout in Fig. 4.1 is for a moderately gassy mine.
Air requirement in each continuous mining section at:
The last open crosscut ¼ 50,000 cfm.
Total for 3 sections ¼ 150,000 cfm.
Air requirement for the longwall:
At the tail gate ¼ 40,000 cfm (a separate split)
At the bleeder shaft ¼ 250,000 cfm
Total air for longwall face ¼ 290,000 cfm
Hence total air at all working faces ¼ 440,000 cfm.
Assuming a ventilation efficiency of 50%, the total capacity of the mine fan(s)
should be approximately 880,000 cfm.